Heavy metal pollution is of great concern. Due to expansion of industrial activities, a large amount of metal is released into the environment, disturbing its fragile balance. Conventional methods of remediation of heavy metal-polluted soil and water are expensive and inefficient. Therefore, new techniques are needed to provide environmentally friendly and highly selective remediation. Streptomycetes, with their unique growth characteristics, ability to form spores and mycelia, and relatively rapid colonization of substrates, act as suitable agents for bioremediation of metals and organic compounds in polluted soil and water. A variety of mechanisms could be involved in reduction of metals in the environment, e.g., sorption to exopolymers, precipitation, biosorption and bioaccumulation. Studies performed on biosorption and bioaccumulation potential of streptomycetes could be used as a basis for further development in this field. Streptomycetes are of interest because of their ability to survive in environments contaminated by metals through the production of a wide range of metal ion chelators, such as siderophores, which provide protection from the negative effects of heavy metals or specific uptake for specialized metabolic processes. Many strains also have the equally important characteristic of resistance to high concentrations of heavy metals.

Technosols are artificial soils generated by diverse human activities and frequently contain toxic substances resulting from industrial processes. Due to lack of nutrients and extreme physico-chemical properties, they represent environments with limited bacterial colonization. Bacterial populations of technosols are dominated usually by Actinobacteria, including streptomycetes, known as a tremendous source of biotechnologically important molecules. In this study, the biodiversity of streptomycete-like isolates from several technosols, mainly mine soils and wastes (landfills and sludge) in Slovakia, was investigated. The combination of basic morphological and biochemical characterisations, including heavy metal resistance determination, and molecular approaches based on 16S rRNA gene analysis were used for the identification of the bacterial strains. From nine isolates of Actinobacteria collected from different habitats, one was found to represent a new species within the Crossiella genus. Eight other isolates were assigned to the genus Streptomyces, of which at least one could represent a new bacterial species. Some isolates showed high resistance to Pb, Zn, Cu or Ni. The most tolerated metal was Pb. The results obtained in this study indicate that technosols are a prospective source of new actinomycete species resistant to heavy metals what underlines their bioremediation potential.

Background: The hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis show how mitochondria can evolve into hydrogenosomes because they possess a mitochondrial genome and parts of an electron-transport chain on the one hand, and a hydrogenase on the other hand. The hydrogenase permits direct reoxidation of NADH because it consists of a [FeFe] hydrogenase module that is fused to two modules, which are homologous to the 24 kDa and the 51 kDa subunits of a mitochondrial complex I. Results: The [FeFe] hydrogenase belongs to a clade of hydrogenases that are different from well-known eukaryotic hydrogenases. The 24 kDa and the 51 kDa modules are most closely related to homologous modules that function in bacterial [NiFe] hydrogenases. Paralogous, mitochondrial 24 kDa and 51 kDa modules function in the mitochondrial complex I in N. ovalis. The different hydrogenase modules have been fused to form a polyprotein that is targeted into the hydrogenosome. Conclusion: The hydrogenase and their associated modules have most likely been acquired by independent lateral gene transfer from different sources. This scenario for a concerted lateral gene transfer is in agreement with the evolution of the hydrogenosome from a genuine ciliate mitochondrion by evolutionary tinkering.

During studies on fructan degradation in the rumen, a Treponema-like bacterium able to utilize Timothy grass fructan, commercial inulin and sucrose a

Two bacterial strains, Am4 and G10 were isolated from rumen fluid of different ruminants: cow (Holstein-Friesian) and sheep (Slovenskè merino), respectively. They were isolated from different hosts and regions, but showed 99.2% similarity of the 16S rRNA genes. Both strains are versatile and ferment various sugars to mainly succinate and lactate and small amounts of acetate and formate. The 16S rRNA sequences of Am4 and G10 revealed that they belonged to the genus Actinomyces, and are related to Actinomyces ruminicola JCM 13352T with 97.0% and 97.4% similarity, respectively. DDH showed strain Am4 and G10 had only 55.8 and 43.3% similarity with the Actinomyces ruminicola JCM 13352T, and had 69.9% similarity among each other. Comparing strain Am4 and G10, gANI value and dDDH were 92.9% and 68.6%, respectively. Additionally, AAI between the strains was 95.8%. MLSA of housekeeping genes showed difference of metG and pheS. The G+C% contents of strain Am4 and G10 were 69.8% and 68.5%, respectively. MK-10(H4) was the principal quinone for strain Am4 (82%) and G10 (91%) with small amounts of MK-10(H8) and MK-10(H6) for both strains. Only MK-9(H4) was detected in strain Am4. MALDI-TOF analysis of protein profiles also revealed that Am4 and G10 are different from each other and from Actinomyces ruminicola JCM 13352T. Based on phylogenetic and physiological characteristics, together with genome comparison and MLSA we propose two novel species in the genus Actinomyces: Actinomyces succiniciruminis sp. nov. (type strain Am4T=TISTR 2317T=DSM 10376T) and Actinomyces glycerinitolerans sp. nov. (type strain G10T=TISTR 2318T=DSM 10377T).